The present invention relates to a vehicular control apparatus that is suitable for an apparatus that executes several engine controls as a fail-safe process to allow a control system to take steps to correct a malfunction when there is an abnormality in a control system of a vehicle.
As electronically controlled vehicle engines become popular, engines and peripheral devices are increasingly controlled by electronic controls using mainly microcomputers.
Examples of such controls are a fuel injection control, which adjusts the injection amount and the injection timing of fuel supplied to cylinders of an engine using fuel injection valves, and an ignition timing control, which adjusts the timing to ignite a mixture of fuel and suction air inside each cylinder using an ignition plug. A system for electrically controlling the opening degree of a throttle valve, which is referred to as an electronic throttle system, is put into a practical use for adjusting the amount of air drawn into the engine. Such a system is also controlled by an electronic control using mainly the microcomputer.
Since such controls are performed by electronic controls, several detailed controls can be performed to maintain the output of an engine to an amount appropriate for the driving condition in each case. On the other hand, controls of manipulation members, such as the fuel injection valves, the ignition plugs, and the throttle valves, are executed by an apparatus that performs the electronic controls, that is, an electronic control unit. Therefore, when an abnormality occurs in the electronic control unit and the controls of the manipulation members are not maintained properly, the engine output might not be maintained properly.
Therefore, in general, when there is an abnormality in the electronic control unit, a first-aid engine control is performed to allow a control system to take steps to correct a malfunction after restricting the maximum output of the engine as a fail-safe process.
A control apparatus that has such fail-safe function is disclosed in the Journal of Technical Disclosure Publication No. 2000-1910 published by Japan Institute of Invention and Innovation. The apparatus is equipped with the above-mentioned electronic throttle system. When it is determined that there is an abnormality in the electronic control unit, a throttle valve is mechanically fixed to a predetermined opening degree by an auxiliary mechanism. This maintains the minimum amount of suction air required for a control system to take steps to correct a malfunction, which further prevents the engine from being stalled. Also, when the control system actually takes steps to correct the malfunction, the engine output is restricted by, for example, reducing the number of cylinders to be driven or correcting the ignition timing.
According to the conventional apparatus, a control system is allowed to take steps to correct a malfunction even if there is an abnormality in the electronic control unit.
However, in the case with the conventional apparatus, restriction of the engine output, such as reducing the number of cylinders to be driven and correcting of the ignition timing, is performed by the electronic control unit that has been determined to have an abnormality. Therefore, there is a fear that the restriction control of the engine output is not executed properly. Thus, there remains room for improvement.